One example of vibration driven movement for a mechanical device is the employment of an internal power source and a vibrating mechanism located in or on the mechanical device. The creation of the movement-inducing vibration is to use rotational motors that spin a shaft attached to an eccentric weight. The rotation of the counterweight induces oscillatory forces. Power sources include wind up springs that are manually powered or DC electric motors. The most recent trend is to use pager motors designed to vibrate a pager or cell phone in silent mode. Well known examples include Vibrobots and Bristlebots, both are small mechanical devices that use vibration to induce movement. The mechanical devices would include legs, generally metal wires or stiff plastic bristles. The vibration causes the entire device to vibrate up and down as well as turn in a single direction and therefore drive in a circle. These mechanical devices tend to drift and turn because no significant directional control is achieved.
Beyond the more widely aforementioned vibration driven mechanical devices there are other devices that could utilize an oscillatory motion to mimic a more dynamic form of movement and which would better correspond to its real-life representation. For example, a snake may be one of the most complex animals to mimic movements in a manner that makes the mechanical device life-like. This may be due to the fact that a snake exhibits four different types of movements, Serpentine, Sidewinding, Rectilinear locomotion, and Concertina.
Serpentine—or an S-shape movement, also known as undulatory locomotion, is used by most snakes on land and in water. Starting at the neck, a snake contracts its muscles, thrusting its body from side to side, creating a series of curves. Sidewinding—by contracting their muscles and flinging their bodies, sidewinders create an S-shape that only has two points of contact with the ground; when they push off, they move laterally. Much of a sidewinding snake's body is off the ground while it moves. Rectilinear locomotion—this technique contracts the body into curves, but these waves are much smaller and curve up and down rather than side to side. When a snake uses rectilinear locomotion, the tops of each curve are lifted above the ground as the ventral scales on the bottoms push against the ground, creating a rippling effect similar to how a caterpillar looks when it walks. Lastly, Concertina—the previous methods work well for horizontal surfaces, but snakes climb using the concertina technique. The snake extends its head and the front of its body along the vertical surface and then finds a place to grip with its ventral scales. To get a good hold, it bunches up the middle of its body into tight curves that grip the surface while it pulls its back end up; it then springs forward again to find a new place to grip with its scales.
To mimic a snake's horizontal movement, mechanical devices need to create the appearance of the life-like Serpentine, Sidewinding, and Rectilinear locomotion. While other mechanical devices have attempted to create mechanical snakes, they typically employ very complex mechanical linkages, gear trains, wheels and multiple motors. There therefore exists a needs to simplify the components while maintaining a high-degree of life like movement.